Introduce a mechanism to dynamically increase vm.min_free_kbytes when critical atomic allocations (GFP_ATOMIC, order-0) fail. This prevents recurring network packet drops or other atomic failures by proactively reserving more memory. The system increases min_free_kbytes by 50% upon failure, capped at 1% of total RAM. To prevent repeated adjustments during burst traffic, a 10-second debounce window is enforced. After traffic subsides, min_free_kbytes automatically decays by 5% every 5 minutes. However, decay stops at 1.2x the initial value rather than returning to baseline. This ensures the system "remembers" previous pressure patterns and avoids repeated failures under similar load. Observed failure logs: [38535641.026406] node 0: slabs: 941, objs: 54656, free: 0 [38535641.037711] node 1: slabs: 349, objs: 22096, free: 272 [38535641.049025] node 1: slabs: 349, objs: 22096, free: 272 [38535642.795972] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535642.805017] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535642.816311] node 0: slabs: 854, objs: 42320, free: 0 [38535642.823066] node 1: slabs: 400, objs: 25360, free: 294 [38535643.070199] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535643.078861] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535643.089719] node 0: slabs: 841, objs: 41824, free: 0 [38535643.096513] node 1: slabs: 393, objs: 24480, free: 272 [38535643.484149] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535643.492831] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535643.503666] node 0: slabs: 898, objs: 43120, free: 159 [38535643.510140] node 1: slabs: 404, objs: 25424, free: 319 [38535644.699224] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535644.707911] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535644.718700] node 0: slabs: 1031, objs: 43328, free: 0 [38535644.725059] node 1: slabs: 339, objs: 17616, free: 317 [38535645.428345] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535645.436888] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535645.447664] node 0: slabs: 940, objs: 40864, free: 144 [38535645.454026] node 1: slabs: 322, objs: 19168, free: 383 [38535645.556122] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535645.564576] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535649.655523] warn_alloc: 59 callbacks suppressed [38535649.655527] swapper/100: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null) [38535649.671692] swapper/100 cpuset=/ mems_allowed=0-1 Signed-off-by: wujing Signed-off-by: Qiliang Yuan --- mm/page_alloc.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 85 insertions(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index c380f063e8b7..2f12d7a9ecbc 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -30,6 +30,7 @@ #include #include #include +#include #include #include #include @@ -3975,6 +3976,16 @@ static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask) mem_cgroup_show_protected_memory(NULL); } +/* Auto-tuning min_free_kbytes on atomic allocation failures (v2) */ +static void decay_min_free_kbytes_workfn(struct work_struct *work); +static void boost_min_free_kbytes_workfn(struct work_struct *work); +static DECLARE_WORK(boost_min_free_kbytes_work, boost_min_free_kbytes_workfn); +static DECLARE_DELAYED_WORK(decay_min_free_kbytes_work, decay_min_free_kbytes_workfn); +static unsigned long last_boost_jiffies = 0; +static int initial_min_free_kbytes = 0; +#define BOOST_DEBOUNCE_MS 10000 /* 10 seconds debounce */ + + void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...) { struct va_format vaf; @@ -4947,6 +4958,17 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, goto retry; } fail: + /* Auto-tuning: trigger boost if atomic allocation fails */ + if ((gfp_mask & GFP_ATOMIC) && order == 0) { + unsigned long now = jiffies; + + /* Debounce: only boost once every 10 seconds */ + if (time_after(now, last_boost_jiffies + msecs_to_jiffies(BOOST_DEBOUNCE_MS))) { + last_boost_jiffies = now; + schedule_work(&boost_min_free_kbytes_work); + } + } + warn_alloc(gfp_mask, ac->nodemask, "page allocation failure: order:%u", order); got_pg: @@ -6526,6 +6548,10 @@ int __meminit init_per_zone_wmark_min(void) refresh_zone_stat_thresholds(); setup_per_zone_lowmem_reserve(); + /* Save initial value for auto-tuning decay mechanism */ + if (initial_min_free_kbytes == 0) + initial_min_free_kbytes = min_free_kbytes; + #ifdef CONFIG_NUMA setup_min_unmapped_ratio(); setup_min_slab_ratio(); @@ -7682,3 +7708,62 @@ struct page *alloc_pages_nolock_noprof(gfp_t gfp_flags, int nid, unsigned int or return page; } EXPORT_SYMBOL_GPL(alloc_pages_nolock_noprof); + +static void boost_min_free_kbytes_workfn(struct work_struct *work) +{ + int new_min; + + /* Cap at 1% of total RAM for safety */ + unsigned long total_kbytes = totalram_pages() << (PAGE_SHIFT - 10); + int max_limit = total_kbytes / 100; + + /* Responsive increase: 50% instead of doubling */ + new_min = min_free_kbytes + (min_free_kbytes / 2); + + if (new_min > max_limit) + new_min = max_limit; + + if (new_min > min_free_kbytes) { + min_free_kbytes = new_min; + /* Update user_min_free_kbytes so it persists through recalculations */ + if (new_min > user_min_free_kbytes) + user_min_free_kbytes = new_min; + + setup_per_zone_wmarks(); + + /* Schedule decay after 5 minutes */ + schedule_delayed_work(&decay_min_free_kbytes_work, + msecs_to_jiffies(300000)); + + pr_info("Auto-tuning: atomic failure, increasing min_free_kbytes to %d\n", + min_free_kbytes); + } +} + +static void decay_min_free_kbytes_workfn(struct work_struct *work) +{ + int new_min; + int decay_floor; + + /* Decay by 5% */ + new_min = min_free_kbytes - (min_free_kbytes / 20); + + /* Don't go below 1.2x initial value (preserve learning effect) */ + decay_floor = initial_min_free_kbytes + (initial_min_free_kbytes / 5); + if (new_min < decay_floor) + new_min = decay_floor; + + if (new_min < min_free_kbytes) { + min_free_kbytes = new_min; + user_min_free_kbytes = new_min; + setup_per_zone_wmarks(); + + /* Schedule next decay if still above floor */ + if (new_min > decay_floor) { + schedule_delayed_work(&decay_min_free_kbytes_work, + msecs_to_jiffies(300000)); + } + + pr_info("Auto-tuning: decaying min_free_kbytes to %d\n", min_free_kbytes); + } +} -- 2.39.5